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Stacie L. Wing-Gaia, Andrew W. Subudhi and Eldon W. Askew

The purpose of this study was to assess the effects of purified oxygenated water on exercise performance under hypoxic conditions. Nine recreational male cyclists (age = 26.6 ± 5.2 y, weight = 87.6 ± 19.5 kg, VO2peak = 46.5 ± 5.9 mL · kg−1 · min−1) completed two 600 kJ cycling time trials under hypoxic conditions (FIO2 = 13.6% O2, Pbar = 641 mmHg) separated by 2 wk. Trials were completed following 3 d ingestion of 35 mL · kg−1 · d−1 of control (CON) or experimental (EXP) water. Time to completion, heart rate (HR), rate of perceived exertion (RPE), pulse oximetry (SaO2), blood gases (PcO2 and PcCO2), and lactate were measured during the trials. Hydration was assessed with pre- and post-exercise body weight and 24-h urine specific gravity. Performance, hydration, and blood oxygenation were unaffected by EXP water. Results of this study suggest that purified oxygenated water does not improve exercise performance in moderately active males.

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Stefan Pettersson and Christina M. Berg

Weight category athletes are known for practicing rapid weight loss before competition weigh-in. After weigh-in, athletes strive to restore euhydration and body mass through food and fluid intake. The aim of the current study was to assess prevalence of hypohydration at competition time among elite athletes’ in four different combat sports, and how water intake and timing of official weigh-in were related to hydration status. Participants were 31 taekwondo practitioners and wrestlers who performed evening weigh-in (EWI) the night before competition day and had thus time for rehydration, and 32 boxers and judokas conducting competition day morning weigh-in (MWI). In total, 32% were female. Urine specific gravity (USG) was measured by refractometry on the competition day’s first morning urine sample. Hypohydration was defined as USG ≥1.020 and serious hypohydration as USG > 1.030. Water intake was measured by means of dietary records. The prevalence of hypohydration was 89% in the morning of competition day. Serious hypohydration was also prevalent. This was found in over 50% of MWI athletes and in 42% of the EWI group. A higher water intake, from both fluids and solid foods, in the evening before competition day was not associated with a more favorable hydration status the following morning. In conclusion, neither weigh-in close to competition nor evening weigh-in with more time for rehydration seems to prevent hypohydration before competition.

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Hannah Bond, Lillian Morton and Andrea J. Braakhuis

Increased plasma nitrate concentrations from dietary sources of nitrate have proven to benefit exercise performance. Beetroot (BR) contains relatively high levels of nitrate (NO3 ), which increases nitric oxide stores. This study investigated whether dietary nitrate supplementation, in the form of a BR beverage, would improve rowing performance during ergometer repetitions. In a randomized crossover design, 14 well-trained junior male rowers consumed 500 ml of either BR or placebo (PL) daily for 6 d. After supplementation, rowers completed 6 maximal 500-m ergometer repetitions and times were recorded. A 7-d washout period separated the 2 trials. Blood pressure, oxygen saturation, maximum heart rate, urine (specific gravity, pH, and nitrites), and lactates were collected for analysis at baseline and pre- and postperformance. Changes in the mean with 95% confidence limits were calculated. There was a likely benefit to average repetition time in the BR condition, compared with PL (0.4%, 95% confidence limits, ± 1.0%). In particular, Repetitions 4–6 showed an almost certain benefit in rowing time on BR (1.7%, 95% CL, ± 1.0%). The underlying mechanism for the observed results remains unknown, as differences observed in rowers’ physiological measures between the 2 conditions were unclear. Conclusively, nitrate supplementation in the form of BR juice resulted in improved maximal rowing-ergometer repetitions, particularly in the later stages of exercise.

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Nora R. Decher, Douglas J. Casa, Susan W. Yeargin, Matthew S. Ganio, Michelle L. Levreault, Catie L. Dann, Camille T. James, Megan A. McCaffrey, Caitlin B. O’Connor and Scott W. Brown

Purpose:

To assess the hydration status and level of hydration knowledge of youths at summer sports camps.

Methods:

Sixty-seven active youths, 57 males (mean ± SD, 12 ± 2 y, 136 ± 16 cm, 50.6 ± 21.1 kg) and 10 females (13 ± 2 y, 153 ± 8 cm, 45.2 ± 9.0 kg) participated in 4 d of sports camp. Hydration status was assessed before the first practice (AM) and after the second practice (PM). Participants completed suriveys assessing hydration knowledge (HAQ) and hydration habits on day 3 and a self-assessment (EQ#1).

Results:

Mean AM urine specific gravity (USG) and urine osmolality (Uosm) scores ranged from minimal to significant dehydration across 4 d, even when temperatures were mild. Correlations between hydration indices and EQ#1, ranging from 0.11 to −0.51, were statistically significant (P < .05), indicating that subjects recognized when they were doing a good or bad job hydrating. HAQ did not correlate strongly with hydration indices suggesting other impediments to hydration. Thirst correlated negatively with EQ#1 (from −0.29 to −0.60).

Conclusion:

Hydration at summer sports camp is a concern and special efforts need to be made to help youths develop hydration strategies.

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Lawrence E. Armstrong, Carl M. Maresh, John W. Castellani, Michael F. Bergeron, Robert W. Kenefick, Kent E. LaGasse and Deborah Riebe

Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color (Ucol) indicates hydration status accurately and to clarify the interchangeability of Ucol, urine osmolality (Uosm), and urine specific gravity (Usg) in research. Ucol, Uosm, and Usg were not significantly correlated with plasma osmolality, plasma sodium, or hemato-crit. This suggested that these hematologic measurements are not as sensitive to mild hypohydration (between days) as the selected urinary indices are. When the data from A, B, and C were combined, Ucol was strongly correlated with Uhg and U„sm. It was concluded that (a) Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) Uosm and Usg may be used interchangeably to determine hydration status.

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Mary Caitlin Stevenson Wilcoxson, Samantha Louise Johnson, Veronika Pribyslavska, James Mathew Green and Eric Kyle O’Neal

Runners are unlikely to consume fluid during training bouts increasing the importance of recovery rehydration efforts. This study assessed urine specific gravity (USG) responses following runs in the heat with different recovery fluid intake volumes. Thirteen male runners completed 3 evening running sessions resulting in approximately 2,200 ± 300 ml of sweat loss (3.1 ± 0.4% body mass) followed by a standardized dinner and breakfast. Beverage fluid intake (pre/postbreakfast) equaled 1,565/2,093 ml (low; L), 2,065/2,593 ml (moderate; M) and 2,565/3,356 mL (high; H). Voids were collected in separate containers. Increased urine output resulted in no differences (p > .05) in absolute mean fluid retention for waking or first postbreakfast voids. Night void averages excluding the first void postrun (1.025 ± 0.008; 1.013 ± 0.008; 1.006 ± 0.003), first morning (1.024 ± 0.004; 1.015 ± 0.005; 1.014 ± 0.005), and postbreakfast (1.022 ± 0.007; 1.014 ± 0.007; 1.008 ± 0.003) USG were higher (p < .05) for L versus M and H respectively and more clearly differentiated fluid intake volume between L and M than color or thirst sensation. Waking (r = -0.66) and postbreakfast (r = -0.71) USG were both significantly correlated (p < .001) with fluid replacement percentage, but not absolute fluid retention. Fluid intake M was reported as most similar to normal consumption (5.6 ± 1.0 on 0–10 scale) after breakfast and equaled 122 ± 16% of sweat losses. Retention data suggests consumption above this level is not warranted or actually practiced by most runners drinking ad libitum, but that periodic prerun USG assessment may be useful for coaches to detect runners that habitually consume low levels of fluids between training bouts in warm seasons.

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J. Luke Pryor, Evan C. Johnson, Jeffery Del Favero, Andrew Monteleone, Lawrence E. Armstrong and Nancy R. Rodriguez

Postexercise protein and sodium supplementation may aid recovery and rehydration. Preserved beef provides protein and contains high quantities of sodium that may alter performance related variables in runners. The purpose of this study was to determine the effects of consuming a commercial beef product postexercise on sodium and water balance. A secondary objective was to characterize effects of the supplementation protocols on hydration, blood pressure, body mass, and running economy. Eight trained males (age = 22 ± 3 y, V̇O2max = 66.4 ± 4.2 ml·kg-1·min-1) completed three identical weeks of run training (6 run·wk-1, 45 ± 6 min·run-1, 74 ± 5% HRR). After exercise, subjects consumed either, a beef nutritional supplement (beef jerky; [B]), a standard recovery drink (SRD), or SRD+B in a randomized counterbalanced design. Hydration status was assessed via urinary biomarkers and body mass. No main effects of treatment were observed for 24 hr urine volume (SRD, 1.7 ± 0.5; B, 1.8 ± 0.6; SRD+B, 1.4 ± 0.4 L·d-1), urine specific gravity (1.016 ± 0.005, 1.018 ± 0.006, 1.017 ± 0.006) or body mass (68.4 ± 8.2, 68.3 ± 7.7, 68.2 ± 8.1 kg). No main effect of treatment existed for sodium intake—loss (-713 ± 1486; -973 ± 1123; -980 ± 1220 mg·d-1). Mean arterial pressure (81.0 ± 4.6, 81.1 ± 7.3, 83.8 ± 5.4 mm Hg) and average exercise running economy (V̇O2: SRD, 47.9 ± 3.2; B, 47.2 ± 2.6; SRD+B, 46.2 ± 3.4 ml·kg-1·min-1) was not affected. Urinary sodium excretion accounted for the daily sodium intake due to the beef nutritional supplement. Findings suggest the commercial beef snack is a viable recovery supplement following endurance exercise without concern for hydration status, performance decrements, or cardiovascular consequences.

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Giannis Arnaoutis, Stavros A. Kavouras, Yiannis P. Kotsis, Yiannis E. Tsekouras, Michalis Makrillos and Costas N. Bardis

There is a lack of studies concerning hydration status of young athletes exercising in the heat.

Purpose:

To assess preexercise hydration status in young soccer players during a summer sports camp and to evaluate bodywater balance after soccer training sessions.

Methods:

Initial hydration status was assessed in 107 young male soccer players (age 11–16 yr) during the 2nd day of the camp. Seventy-two athletes agreed to be monitored during 2 more training sessions (3rd and 5th days of the camp) to calculate dehydration via changes in body weight, while water drinking was allowed ad libitum. Hydration status was assessed via urine specific gravity (USG), urine color, and changes in total body weight. Mean environmental temperature and humidity were 27.2 ± 2 °C and 57% ± 9%, respectively.

Results:

According to USG values, 95 of 107 of the players were hypohydrated (USG ≥ 1.020) before practice. The prevalence of dehydration observed was maintained on both days, with 95.8% and 97.2% of the players being dehydrated after the training sessions on the 3rd and 5th days, respectively. Despite fluid availability, 54 of the 66 (81.8%) dehydrated players reduced their body weight (–0.35 ± 0.04 kg) as a response to training, while 74.6% (47 out of the 63) further reduced their body weight (–0.22 ± 0.03 kg) after training on the 5th day.

Conclusion:

Approximately 90% of the young soccer players who began exercising under warm weather conditions were hypohydrated, while drinking ad libitum during practice did not prevent further dehydration in already dehydrated players.

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J.D. Adams, Stavros A. Kavouras, Evan C. Johnson, Lisa T. Jansen, Catalina Capitan-Jimenez, Joseph I. Robillard and Andy Mauromoustakos

The purpose of this investigation was to quantify the effects of storage temperature, duration, and the urinary sediment on urinary hydration markers. Thirty-six human urine samples were analyzed fresh and then the remaining sample was separated into 24 separate vials, six in each of the following four temperatures: 22 °C, 7 °C, -20 °C, and -80 °C. Two of each sample stored in any given temperature, were analyzed after 1, 2, and 7 days either following vortexing or centrifugation. Each urine sample was analyzed for osmolality (UOsm), urine specific gravity (USG), and urine color (UC). UOsm was stable at 22 °C, for 1 day (+5–9 mmol∙kg-1, p > .05) and at 7 °C, UOsm up to 7 days (+8–8 mmol∙kg-1, p > .05). At -20 and -80 °C, UOsm decreased after 1, 2, and 7 days (9–61 mmol∙kg-1, p < .05). Vortexing the sample before analysis further decreased only UOsm in the -20 °C and -80 °C storage. USG remained stable up to 7 days when samples were stored in 22 °C or 7 °C (p > .05) but declined significantly when stored in -20 °C, and -80 °C (p < .001). UC was not stable in any of the storing conditions for 1, 2, and 7 days. In conclusion, these data indicate that urine specimens analyzed for UOsm or USG remained stable in refrigerated (7 °C) environment for up to 7 days, and in room temperature for 1 day. However, freezing (-20 and -80 °C) samples significantly decreased the values of hydration markers.

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Bjoern Geesmann, Joachim Mester and Karsten Koehler

Athletes competing in ultra-endurance events are advised to meet energy requirements, to supply appropriate amounts of carbohydrates (CHO), and to be adequately hydrated before and during exercise. In practice, these recommendations may not be followed because of satiety, gastrointestinal discomfort, and fatigue. The purpose of the study was to assess energy balance, macronutrient intake and hydration status before and during a 1,230-km bike marathon. A group of 14 well-trained participants (VO2max: 63.2 ± 3.3 ml/kg/min) completed the marathon after 42:47 hr. Ad libitum food and fluid intake were monitored throughout the event. Energy expenditure (EE) was derived from power output and urine and blood markers were collected before the start, after 310, 618, and 921 km, after the finish, and 12 hr after the finish. Energy intake (EI; 19,749 ± 4,502 kcal) was lower than EE (25,303 ± 2,436 kcal) in 12 of 14 athletes. EI and CHO intake (average: 57.1 ± 17.7 g/hr) decreased significantly after km 618 (p < .05). Participants ingested on average 392 ± 85 ml/hr of fluid, but fluid intake decreased after km 618 (p < .05). Hydration appeared suboptimal before the start (urine specific gravity: 1.022 ± 0.010 g/ml) but did not change significantly throughout the event. The results show that participants failed to maintain in energy balance and that CHO and fluid intake dropped below recommended values during the second half of the bike marathon. Individual strategies to overcome satiety and fatigue may be necessary to improve eating and drinking behavior during prolonged ultra-endurance exercise.